1. Field of the Invention
This invention relates to a Ni-based alloy which is excellent in anti-corrosion properties, in particular anti-pitting corrosion property and anti-crevice corrosion property in an environment containing chlorine ions, as well as in workability, in particular workability in hot working.
2. Conventional Art
Ni-based alloys having excellent anti-corrosion properties have hitherto been used in the manufacture of exhaust gas desulfurizers for chemical plants, electroplating devices, boilers or the like; structural members for semiconductor devices; food processing devices; medical equipment; and various cutter blades and manual tools which are exposed to sea water; or the like.
Ni-based alloys conventionally known as such anti-corrosive alloys include a Ni-based alloy (hereinafter referred to as "alloy 55C") disclosed in Japanese Patent Application, Laid-Open (First-Publication) No. 62-40337, and consisting of 30.1 weight % of Cr, 20.3 weight % of Mo, balance Ni and unavoidable impurities; a Ni-based alloy (hereinafter referred to as "alloy 625") disclosed in U.S. Pat. No. 3,160,500 and consisting of 21.5 weight % of Cr, 9 weight % of Mo, 2.5 weight % of Fe, 3.7 weight % of Nb, balance Ni and unavoidable impurities; a Ni-based alloy (hereinafter referred to as "alloy C-276") disclosed in U.S. Pat. No. 3,203,792 and consisting of 16.1 weight % of Cr, 16.2 weight % of Mo, 5.2 weight % of Fe, 3.2 weight % of W, balance Ni and unavoidable impurities; and a Ni-based alloy (hereinafter referred to as "alloy C-22") disclosed in U.S. Pat. No. 4,533,414 and consisting of 21.5 weight % of Cr, 13.2 weight % of Mo, 4.1 weight % of Fe, 3.1 weight % of W, balance Ni and unavoidable impurities.
However, the demands for the anti-corrosive Ni-based alloys having more excellent anti-corrosion properties and workability have been increasing because anti-corrosive Ni alloys are being utilized in progressively severe environments in recent years, and because the devices employed in such environments have come to have more complicated shapes. The aforesaid conventional Ni-based alloys are therefore not satisfactory. More specifically, "alloy 625", "alloy C-276" and "alloy C-22" exhibit excellent workability in hot working, but are inferior in anti-corrosion properties, in particular anti-pitting corrosion property and anti-crevice corrosion property in an environment containing chlorine ions. In contrast, "alloy 55C" exhibits excellent anti-corrosion properties in the environment containing chlorine ions, but is inferior in workability in hot working operation.